The U.S. Department of Energy as well as sustainable construction organizations and the like are pressing for the installation of dynamic daylighting and shading systems to improve energy efficiency in buildings. Innovations are sorely needed to meet this need.
Various types of transparent and translucent glazing systems are available for the construction of horizontal, vertical and sloped glazing in skylights, roofs, walls, and other architectural structures designed to pass light for daylighting interiors or other purposes. When using such glazing systems, it is therefore desirable, in accord with sustainable construction criteria, to optimize the system's shading coefficient to reduce solar heat gain on hot summer days and during peak sunlight hours year round, while providing maximum light and solar heating on cold winter days and when it is otherwise needed or desired. It is also often desirable to control glare and direct sunlight in order to ensure the comfort of those who occupy the space exposed to the glazing system. If architects and space planners can be freed from the constraints of current light transmission control in horizontal, vertical and sloped glazing in skylights, roofs, walls, and other architectural structures, they will be able to maximize interior daylight without the burden of unmanaged heat gain or discomforting glare more effectively address these shading requirements and meet sustainable construction criteria. Furthermore, these considerations apply as well to shading of open unglazed areas.
Indeed, if the level of light entering overhead large glazed as well as unglazed areas can be simply, efficiently, effectively and uniformly controlled with little or no light leakage between, e.g., multiple adjacent light-controlling members, it will provide architects and space planners with important new tools. They will be able to maximize energy efficiency with aesthetic and sustainable designs to a degree not previously possible. And, sun tracking control shading systems can dynamically rotate light-blocking members up to 360° to efficiently shade small or large glazed and open, unglazed areas to provide the desired uniform light level inside the space thereunder would be particularly desirable.
The known approaches to controlling the amount of light admitted through glazing systems—particularly on a large scale and in overhead, horizontal and sloped glazing applications—are limited and are generally unreliable, noisy and often difficult and expensive to construct, assemble on-site, maintain and service. Also, existing approaches suffer from non-uniform and excessive light leakage between adjacent light-controlling members which appears as an aesthetically undesirable series of often irregular bright lines. Additionally, although it is often desirable to retrofit light-controlling systems to already constructed glazing systems, this is not easily accomplished with current light-controlling systems. There is therefore substantial need for an economic and readily constructed and retrofitted light-controlling system that may be used for shading glazed areas of all sizes, including very large glazed areas. There is also substantial need for such light-controlling systems that can be easily assembled, maintained and serviced, in which the light is uniformly distributed across the glazed area, and in which light leakage is de minimis or eliminated or, where present, is kept to narrow and regular lines.
Prior approaches to controlling the level of light passing into architectural structures have included louver blind assemblies using pivoting flexible light-controlling members operable behind a window or sandwiched inside a chamber formed by a double-glazed window unit. Such louver blinds require substantial support of the flexible members which, additionally, must be controlled from both their distal and their proximal ends. Furthermore, louver blinds are difficult and expensive to assemble, apply, operate, maintain and replace, and cannot be readily adapted for use in non-vertical applications or in applications in which it is either desirable or necessary to control the flexible members from only one end. Louver blinds are particularly problematic when it comes to applications in which the installation requiring light-control or shading is very long, e.g., 10 ft., 20 ft., 40 ft., 60 ft. or more. In addition, dynamic control of louver blinds in large overhead shading applications is complicated, expensive, difficult to install and maintain, and often simply impractical. Furthermore, rotating louver blinds require that rotary force be applied to the top edge of the blinds. This is because louver blinds are flexible and rely on the force of gravity to hang vertically in the proper desired position and therefore cannot be rotated from their base. Thus, louver blinds cannot be used in generally horizontal overhead glazing application or in sloped applications, where rotation must be controlled from the base or proximal end and the force of gravity on non-vertical louver blinds would create untold complications and very non-uniform shading.
Other approaches to controlling the level of light passing through architectural structures have used motorized shades or drapery. These approaches are also problematic, particularly in the applications noted above where the glazing is large and would require very long shades or blinds, e.g., on the order of 10 ft., 20 ft., 40 ft., 60 ft. or more, since such large shades would be heavy, difficult to manipulate and maintain, and expensive. The mechanics of controlling and manipulating motorized shades or drapery of any size is quite complicated and therefore motorized shades and drapery are expensive and difficult to maintain. Also, it is not possible to achieve uniform light distribution across a wide glazed space with motorized shades or drapery.
U.S. Pat. Nos. 7,281,353; 6,499,255; and 6,978,578 provide other more recent approaches to addressing the challenge of providing dynamic daylighting and shading systems on a large scale and in overhead, horizontal and sloped glazing applications. These patents utilize a plurality of rotatably-mounted light-blocking tubular members having at least one portion that is substantially opaque and means for rotating the light-blocking members to block out varying amounts of radiation by varying the area of the opaque portions presented to the incoming light. In the systems described in the above three patents, the light-blocking members are combined in a series of adjacent segregated elongated tubular cells or mounted for rotation in individual or paired cross-members positioned between light transmitting panels. As an alternative to tubular members, a generally rigid opaque member may be used if fitted with rings spaced along this member. Indeed, even the tubular members may be fitted with such rings in order to facilitate tubular member rotation and to improve performance. Attachment of the rings requires notching of the generally rigid opaque member and can be difficult and time-consuming for both generally flat and tubular members. Also, the rings, which unfortunately may interfere with light-blocking, must nevertheless be wide enough to accommodate longitudinal movement due to thermal expansion and contraction. Determining the width and location of the rings and ring-receiving notches is complex and, indeed, may require architectural approval before being implemented in custom applications, often making the use of such rings inconvenient and expensive.
In the system of the '578 patent, the centers of rotation of the light-blocking members do not remain in place as the light-blocking members are rotated resulting in increased torque and load on the motor and varying horizontal positioning of the light-controlling members. Since the light-blocking members often do not run true because they are inadequately restrained and therefore bend and snake about as they rotate, they produce uneven and continuously varying spacing between adjacent members with uneven light distribution and an unacceptable appearance of disarray of the light-blocking members. When these light-blocking members are used in vertically oriented applications, they can disengage from lower-cross-members and run far more untrue with even greater increases in the torque/motor load and irregular lateral movement. When they are used in applications calling for an inclined orientation, the light-blocking members tend to disengage from the lower cross members and rotate in an uncontrolled manner, rubbing against one another, resulting in increased friction and torque and producing problematic noise. Finally, in tests simulating the application of snow and wind loads, excessive friction is produced between the light-blocking members and the cross-members which could cause early failure.
The paired upper and lower cross members of the '353 patent solve the above problems. Also, when this system is in the fully closed position, there may be more light leakage than often desired.
While the designs provided by the above three patents represent important advances in the art, they have another drawback. For these designs, the light-blocking components of adjacent tubular members cannot come sufficiently close to each other when the systems are in their fully closed configuration due to intervening structural features. Therefore total blackout or near total blackout light blocking cannot be achieved.
We provide a significantly improved design in one of our two patent applications, U.S. patent application Ser. No. 12/903,904 filed Oct. 13, 2010. In the '904 application, a beam with adjacent bores separated by web portions is described. Bearing members comprising an annular ring are dimensioned to fit within the bores and are provided with a flange extending radially outwardly from the rings. The bearings are mounted to the beam with the flanges in an offset fashion. A first bearing member is mounted in a first bore with its flange adjacent to a first beam face, its ring extending into the bore and a next bearing member mounted in a next adjacent bore with its flange adjacent the opposite beam face and its ring extending into the bore. This bearing structure and disposition makes it possible to bring the edges of adjacent light-controlling members close together when the members are closed making them more effective in light-blocking than has heretofore been thought possible.
However, in various applications, including where the web portions in the beam of the '904 application between the bores are increased in width for structural or other reasons, it is desirable to provide alternative embodiments to achieve total or near total blackout where the adjacent edges of the light-blocking members are able to span the increased width webs between adjacent bores.
The present system provides a transparent/translucent panel unit in which the transmission of light across the system can be adjusted from almost full transparency or translucency to near total opacity.